Furan-2,5-dicarboxylic acid purge process

ABSTRACT

Disclosed is an oxidation process to produce a crude carboxylic acid product carboxylic acid product. The process comprises oxidizing a feed stream comprising at least one oxidizable compound to generate a crude carboxylic acid slurry comprising furan-2,5-dicarboxylic acid (FDCA) and compositions thereof. Also disclosed is a process to produce a dry purified carboxylic acid product by utilizing various purification methods on the crude carboxylic acid.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/990,140 filed May 8, 2014, the entire disclosureof which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

Aromatic dicarboxylic acids such as terephthalic acid and isophthalicacid or their di-esters, dimethyl terephthalate as for example, are usedto produce a variety of polyester products, important examples of whichare poly(ethylene terephthalate) and its copolymers. The aromaticdicarboxylic acids are synthesized by the catalytic oxidation of thecorresponding dialkyl aromatic compounds which are obtained from fossilfuels (US 2006/0205977 A1). Esterification of these diacids using excessalcohol produces the corresponding di-esters (US2010/0210867A1). Thereis a growing interest in the use of renewable resources as feed stocksfor the chemical industries mainly due to the progressive reduction offossil reserves and their related environmental impacts.

Furan-2,5-dicarboxylic acid (FDCA) is a versatile intermediateconsidered as a promising closest biobased alternative to terephthalicacid and isophthalic acid. Like aromatic diacids, FDCA can be condensedwith diols such as ethylene glycol to make polyester resins similar topolyethylene terephthalate (PET) (Gandini, A.; Silvestre, A. J; Neto, C.P.; Sousa, A. F.; Gomes, M., J. Poly. Sci. A 2009, 47, 295). FDCA hasbeen prepared by oxidation of 5-(hydroxymethyl) furfural (5-HMF) underair using homogenous catalysts (US2003/0055271 A1 and Partenheimer, W.;Grushin, V. V., Adv. Synth. Catal. 2001, 343, 102-111.) but only amaximum of 44.8% yield using a Co/Mn/Br catalyst system and a maximum of60.9% yield was reported using Co/Mn/Br/Zr catalysts combination.Recently, we reported a process for producing furan-2,5-dicarboxylicacid (FDCA) in high yields by liquid phase oxidation of 5-HMF or itsderivatives using a Co/Mn/Br catalyst system that minimizes solvent andstarting material loss through carbon burn (U.S. patent application Ser.Nos. 13/228,803, 13/228,809, 13/228,816, and Ser. No. 13/228,799, hereinincorporated by reference).

Disclosed is a method for recovering a portion of oxidation solvent, aportion of oxidation catalyst, and removing a portion of oxidationby-products and raw material impurities from a solvent stream generatedin a process to make furan-2,5-dicarboxylic acid (FDCA). The processcomprises oxidizing a feed stream comprising at least one oxidizablecompound selected from the following group: 5-(hydroxymethyl)furfural(5-HMF), 5-HMF esters (5-R(CO)OCH₂-furfural where R=alkyl, cycloalkyland aryl), 5-HMF ethers (5-R′OCH₂-furfural, where R′=alkyl, cycloalkyland aryl), 5-alkyl furfurals (5-R″-furfural, where R″=alkyl, cycloalkyland aryl), mixed feed-stocks of 5-HMF and 5-HMF esters and mixedfeed-stocks of 5-HMF and 5-HMF ethers and mixed feed-stocks of 5-HMF and5-alkyl furfurals to generate a crude carboxylic acid slurry comprisingfuran-2,5-dicarboxylic acid (FDCA) in an oxidation zone, cooling a crudecarboxylic acid slurry in a cooling zone to generate a cooled crudecarboxylic acid slurry, removing impurities from a cooled crudecarboxylic acid slurry in a solid-liquid separation zone to form a lowimpurity carboxylic acid stream and a mother liquor stream, routing atleast a portion of the mother liquor stream to a mother liquor purgezone to generate a recycle oxidation solvent stream, a recycle catalystrich stream, a raffinate stream, and an impurity rich waste stream.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates different embodiments of the invention wherein aprocess to produce a dried carboxylic acid 410 is provided.

FIG. 2 illustrates an embodiment of the invention, wherein an purgestream is created. This figure is a detailed illustration on zone 700 inFIG. 1.

DETAILED DESCRIPTION

It should be understood that the following is not intended to be anexclusive list of defined terms. Other definitions may be provided inthe foregoing description, such as, for example, when accompanying theuse of a defined term in context.

As used herein, the terms “a,” “an,” and “the” mean one or more.

As used herein, the term “and/or,” when used in a list of two or moreitems, means that any one of the listed items can be employed by itselfor any combination of two or more of the listed items can be employed.For example, if a composition is described as containing components A,B, and/or C, the composition can contain A alone; B alone; C alone; Aand B in combination; A and C in combination, B and C in combination; orA, B, and C in combination.

As used herein, the terms “comprising,” “comprises,” and “comprise” areopen-ended transition terms used to transition from a subject recitedbefore the term to one or more elements recited after the term, wherethe element or elements listed after the transition term are notnecessarily the only elements that make up the subject.

As used herein, the terms “having,” “has,” and “have” have the sameopen-ended meaning as “comprising,” “comprises,” and “comprise” providedabove.

As used herein, the terms “including,” “includes,” and “include” havethe same open-ended meaning as “comprising,” “comprises,” and “comprise”provided above.

The present description uses numerical ranges to quantify certainparameters relating to the invention. It should be understood that whennumerical ranges are provided, such ranges are to be construed asproviding literal support for claim limitations that only recite thelower value of the range as well as claim limitations that only recitethe upper value of the range. For example, a disclosed numerical rangeof 10 to 100 provides literal support for a claim reciting “greater than10” (with no upper bounds) and a claim reciting “less than 100” (with nolower bounds).

The present description uses specific numerical values to quantifycertain parameters relating to the invention, where the specificnumerical values are not expressly part of a numerical range. It shouldbe understood that each specific numerical value provided herein is tobe construed as providing literal support for a broad, intermediate, andnarrow range. The broad range associated with each specific numericalvalue is the numerical value plus and minus 60 percent of the numericalvalue, rounded to two significant digits. The intermediate rangeassociated with each specific numerical value is the numerical valueplus and minus 30 percent of the numerical value, rounded to twosignificant digits. The narrow range associated with each specificnumerical value is the numerical value plus and minus 15 percent of thenumerical value, rounded to two significant digits. For example, if thespecification describes a specific temperature of 62° F., such adescription provides literal support for a broad numerical range of 25°F. to 99° F. (62° F.+/−37° F.), an intermediate numerical range of 43°F. to 81° F. (62° F.+/−19° F.), and a narrow numerical range of 53° F.to 71° F. (62° F.+/−9° F.). These broad, intermediate, and narrownumerical ranges should be applied not only to the specific values, butshould also be applied to differences between these specific values.Thus, if the specification describes a first pressure of 110 psia and asecond pressure of 48 psia (a difference of 62 psi), the broad,intermediate, and narrow ranges for the pressure difference betweenthese two streams would be 25 to 99 psi, 43 to 81 psi, and 53 to 71 psi,respectively

One embodiment of the present invention is illustrated in FIGS. 1 and 2.The present invention provides a process for recovering a portion ofoxidation solvent, a portion of oxidation catalyst, and removing aportion of oxidation by-products and raw material impurities from asolvent stream generated in a process to make furan-2,5-dicarboxylicacid (FDCA).:

Step (a) comprises feeding oxidation solvent, a catalyst system, a gasstream comprising oxygen, and oxidizable raw material comprising atleast one compound selected from the group of formula:5-(hydroxymethyl)furfural (5-HMF), 5-HMF esters (5-R(CO)OCH₂-furfuralwhere R=alkyl, cycloalkyl and aryl), 5-HMF ethers (5-R′OCH₂-furfural,where R′=alkyl, cycloalkyl and aryl), 5-alkyl furfurals (5-R″-furfural,where R″=alkyl, cycloalkyl and aryl), mixed feed-stocks of 5-HMF and5-HMF esters, mixed feed-stocks of 5-HMF and 5-HMF ethers, and mixedfeed-stocks of 5-HMF and 5-alkyl furfurals to an oxidation zone 100 togenerate a crude carboxylic acid slurry 110 comprisingfuran-2,5-dicarboxylic (FDCA).

Structures for the preferred oxidizable raw material compounds areoutlined below:

5-HMF feed is oxidized with elemental O₂ in a multi-step reaction toform FDCA with 5-formyl furan-2-carboxyic acid (FFCA) as a keyintermediate (Eq 1). Oxidation of 5-(acetoxymethyl)furfural (5-AMF),which contains an oxidizable ester and aldehydes moieties, producesFDCA, FFCA, and acetic acid (Eq 2). Similarly, oxidation of5-(ethoxymethyl)furfural (5-EMF) produces FDCA, FFCA,5-(ethoxycarbonyl)furan-2-carboxylic acid (EFCA) and acetic acid (Eq 3).

Streams routed to the primary oxidation zone 100 comprise gas stream 10comprising oxygen, and stream 30 comprising oxidation solvent, andstream 20 comprising oxidizable raw material. In another embodiment,streams routed to the oxidization zone 100 comprise gas stream 10comprising oxygen and stream 20 comprising oxidation solvent, catalyst,and oxidizable raw material. In yet another embodiment, the oxidationsolvent, gas comprising oxygen, catalyst system, and oxidizable rawmaterials can be fed to the oxidization zone 100 as separate andindividual streams or combined in any combination prior to entering theoxidization zone 100 wherein said feed streams may enter at a singlelocation or in multiple locations into oxidizer zone 100.

Suitable catalyst systems is at least one compound selected from, butare not limited to, cobalt, bromine, and manganese compounds, which aresoluble in the selected oxidation solvent. The preferred catalyst systemcomprises cobalt, manganese and bromine wherein the weight ratio ofcobalt to manganese in the reaction mixture is from about 10 to about400 and the weight ratio of cobalt to bromine is from about 0.7 to about3.5. Data shown in Tables 1 to 3 demonstrate that very high yield ofFDCA can be obtained using 5-HMF or its derivatives using the catalystcomposition described above.

Suitable oxidation solvents include, but are not limited to, aliphaticmono-carboxylic acids, preferably containing 2 to 6 carbon atoms, andmixtures thereof, and mixtures of these compounds with water. In oneembodiment, the oxidation solvent comprises acetic acid wherein theweight % of acetic acid in the oxidation solvent is greater than 50%,greater than 75%, greater than 85%, and greater than 90%. In anotherembodiment, the oxidation solvent comprises acetic acid and waterwherein the proportions of acetic acid to water is greater than 1:1,greater than 6:1, greater than 7:1, greater than 8:1, and greater than9:1.

The temperature in oxidation zone can range from 100° C. to 220° C., or100° C. to 200° C., or 130° C. to 180° C., or 100° C. to 180° C. and canpreferably range from 110° C. to 160° C. In another embodiment, thetemperature in oxidation zone can range from 105° C. to 140° C.

One advantage of the disclosed oxidation conditions is low carbon burnas illustrated in Tables 1 to 3. Oxidizer off gas stream 120 is routedto the oxidizer off gas treatment zone 800 to generate an inert gasstream 810, liquid stream 820 comprising water, and a recoveredoxidation solvent stream 830 comprising condensed solvent. In oneembodiment, at least a portion of recovered oxidation solvent stream 830is routed to wash solvent stream 320 to become a portion of the washsolvent stream 320 for the purpose of washing the solids present in thesolid-liquid separation zone. In another embodiment, the inert gasstream 810 can be vented to the atmosphere. In yet another embodiment,at least a portion of the inert gas stream 810 can be used as an inertgas in the process for inerting vessels and or used for convey gas forsolids in the process. In another embodiment, at least a portion of theenergy in stream 120 is recovered in the form of steam and orelectricity.

In another embodiment of the invention, a process is provided forproducing furan-2,5-dicarboxylic acid (FDCA) in high yields by liquidphase oxidation that minimizes solvent and starting material lossthrough carbon burn. The process comprises oxidizing at least oneoxidizable compound in an oxidizable raw material stream 30 in thepresence of an oxidizing gas stream 10, oxidation solvent stream 20, andat least one catalyst system in a oxidation zone 100; wherein theoxidizable compound is 5-(hydroxymethyl)furfural (5-HMF); wherein thesolvent stream comprises acetic acid with or without the presence ofwater; wherein the catalyst system comprising cobalt, manganese, andbromine, wherein the weight ratio of cobalt to manganese in the reactionmixture is from about 10 to about 400. In this process, the temperaturecan vary from about 100° C. to about 220° C., from about 105° C. toabout 180° C., and from about 110° C. to about 160° C. The cobaltconcentration of the catalyst system can range from about 1000 ppm toabout 6000 ppm, and the amount of manganese can range from about 2 ppmto about 600 ppm, and the amount of bromine can range from about 300 ppmto about 4500 ppm with respect to the total weight of the liquid in thereaction medium.

Step (b) comprises routing the crude carboxylic acid slurry 110comprising FDCA to cooling zone 200 to generate a cooled crudecarboxylic acid slurry stream 210 and a 1^(st) vapor stream 220comprising oxidation solvent vapor. The cooling of crude carboxylicslurry stream 110 can be accomplished by any means known in the art.Typically, the cooling zone 200 comprises a flash tank. In anotherembodiment, a portion up to 100% of the crude carboxylic acid slurrystream 110 is routed directly to solid-liquid separation zone 300, thussaid portion up to 100% is not subjected to cooling in cooling zone 200.The temperature of stream 210 can range from 35° C. to 210° C., 55° C.to 120° C., and preferably from 75° C. to 95° C.

Step (c) comprises isolating, washing, and dewatering solids present inthe cooled crude carboxylic acid slurry stream 210 in the solid-liquidseparation zone 300 to generate a crude carboxylic acid wet cake stream310 comprising FDCA. These functions may be accomplished in a singlesolid-liquid separation device or multiple solid-liquid separationdevices. The solid-liquid separation zone comprises at least onesolid-liquid separation device capable of separating solids and liquids,washing solids with a wash solvent stream 320, and reducing the %moisture in the washed solids to less than 30 weight %, less than 20weight %, less than 15 weight %, and preferably less than 10 weight %.

Equipment suitable for the solid liquid separation zone can typically beat least one of the following types of devices: centrifuge, cyclone,rotary drum filter, belt filter, pressure leaf filter, candle filter,and the like. The preferred solid liquid separation device for the solidliquid separation zone is a rotary pressure drum filter.

The temperature of cooled crude carboxylic acid slurry steam 210 whichis routed to the solid-liquid separation zone 300 can range from 35° C.to 210° C., 55° C. to 120° C., and is preferably from 75° C. to 95° C.Wash solvent stream 320 comprises a liquid suitable for displacing andwashing mother liquor from the solids. In one embodiment, a suitablewash solvent comprises acetic acid. In another embodiment, a suitablewash solvent comprises acetic acid and water. In yet another embodiment,a suitable wash solvent comprises water and can be 100% water. Thetemperature of the wash solvent can range from 20° C. to 160° C., 40° C.to 110° C., and preferably from 50° C. to 90° C.

The amount of wash solvent used is defined as the wash ratio and equalsthe mass of wash divided by the mass of solids on a batch or continuousbasis. The wash ratio can range from about 0.3 to about 5, about 0.4 toabout 4, and preferably from about 0.5 to 3. After solids are washed inthe solid liquid separation zone, they are dewatered. Dewateringinvolves reducing the mass of moisture present with the solids to lessthan 30% by weight, less than 25% by weight, less than 20% by weight,and most preferably less than 15% by weight resulting in the generationof a crude carboxylic acid wet cake stream 310 comprising FDCA.

In one embodiment, dewatering is accomplished in a filter by passing astream comprising gas through the solids to displace free liquid afterthe solids have been washed with a wash solvent. In an embodiment,dewatering of the wet cake solids in solid-liquid separation zone 300can be implemented before washing and after washing the wet cake solidsin zone 300 to minimize the amount of oxidizer solvent present in thewash liquor stream 340. In another embodiment, dewatering is achieved bycentrifugal forces in a perforated bowl or solid bowl centrifuge.

The mother liquor steam 330 generated in solid-liquid separation zone300 comprises oxidation solvent, catalyst, and impurities. From 5 wt %to 95 wt %, from 30 wt % to 90 wt %, and most preferably from 40 wt % to80 wt % of mother liquor present in the crude carboxylic acid slurry 110is isolated in solid-liquid separation zone 300 to generate motherliquor stream 330 resulting in dissolved matter comprising impuritiespresent in mother liquor stream 330 not going forward in the process.

In one embodiment, a portion of mother liquor stream 330 is routed to amother liquor purge zone 700, wherein a portion is at least 5 weight %,at least 25 weight %, at least 45 weight %, at least 55 weight % atleast 75 weight %, or at least 90 weight %. In another embodiment, atleast a portion of the mother liquor stream 330 is routed back to theoxidation zone 100, wherein a portion is at least 5 weight %. In yetanother embodiment, at least a portion of mother liquor stream 330 isrouted to a mother liquor purge zone 700 and to the oxidation zone 100wherein a portion is at least 5 weight %. In one embodiment, the motherliquor purge zone 700 comprises an evaporative step to separateoxidation solvent from stream 330 by evaporation. Solids can be presentin mother liquor stream 330 ranging from about 5 weight % to about 0.5weight %. In yet another embodiment, any portion of mother liquor stream330 routed to a mother liquor purge zone is first subjected to a solidliquid separation device to control solids present in stream 330 to lessthan 1 wt %, less than 0.5 wt %, less than 0.3 wt %, or less than 0.1%by weight. Suitable solid liquid separation equipment comprise a discstack centrifuge and batch pressure filtration solid liquid separationdevices. A preferred solid liquid separation device for this applicationcomprises a batch candle filter.

Wash liquor stream 340 is generated in the solid-liquid separation zone300 and comprises a portion of the mother liquor present in stream 210and wash solvent wherein the ratio of mother liquor mass to wash solventmass is less than 3 and preferably less than 2. In an embodiment, atleast a portion of wash liquor stream 340 is routed to oxidation zone100 wherein a portion is at least 5 weight %. In an embodiment, at leasta portion of wash liquor stream is routed to mother liquor purge zone700 wherein a portion is at least 5 weight %. In another embodiment, atleast a portion of wash liquor stream 340 is routed to oxidation zone100 and mother liquor purge zone 700 wherein a portion is at least 5weight %.

In another embodiment, at least a portion of the crude carboxylic acidslurry stream 110 up to 100 weight % is routed directly to thesolid-liquid separation zone 300, thus this portion will bypass thecooling zone 200. In this embodiment, feed to the solid-liquidseparation zone 300 comprises at least a portion of the crude carboxylicacid slurry stream 110 and wash solvent stream 320 to generate a crudecarboxylic acid wet cake stream 310 comprising FDCA. Solids in the feedslurry are isolated, washed, and dewatered in solid-liquid separationzone 300. These functions may be accomplished in a single solid-liquidseparation device or multiple solid-liquid separation devices. Thesolid-liquid separation zone comprises at least one solid-liquidseparation device capable of separating solids and liquids, washingsolids with a wash solvent stream 320, and reducing the % moisture inthe washed solids to less than 30 weight %, less than 20 weight %, lessthan 15 weight %, and preferably less than 10 weight %. Equipmentsuitable for the solid liquid separation zone can typically be at leastone of the following types of devices: centrifuge, cyclone, rotary drumfilter, belt filter, pressure leaf filter, candle filter, and the like.The preferred solid liquid separation device for the solid liquidseparation zone 300 is a continuous rotary pressure drum filter. Thetemperature of the crude carboxylic acid slurry stream, which is routedto the solid-liquid separation zone 300 can range from 40° C. to 210°C., 60° C. to 170° C., ° C. and is preferably from 80° C. to 160° C. Thewash stream 320 comprises a liquid suitable for displacing and washingmother liquor from the solids. In one embodiment, a suitable washsolvent comprises acetic acid and water. In another embodiment, asuitable wash solvent comprises water up to 100% water. The temperatureof the wash solvent can range from 20° C. to 180° C., 40° C. and 150°C., and preferably from 50° C. to 130° C. The amount of wash solventused is defined as the wash ratio and equals the mass of wash divided bythe mass of solids on a batch or continuous basis. The wash ratio canrange from about 0.3 to about 5, about 0.4 to about 4, and preferablyfrom about 0.5 to 3.

After solids are washed in the solid liquid separation zone, they aredewatered. Dewatering involves reducing the mass of moisture presentwith the solids to less than 30% by weight, less than 25% by weight,less than 20% by weight, and most preferably less than 15% by weightresulting in the generation of a crude carboxylic acid wet cake stream310. In one embodiment, dewatering is accomplished in a filter bypassing a gas stream through the solids to displace free liquid afterthe solids have been washed with a wash solvent. In another embodiment,the dewatering of the wet cake in solid-liquid separation zone 300 canbe implemented before washing and after washing the solids in zone 300to minimize the amount of oxidizer solvent present in the wash liquorstream 340 by any method known in the art. In yet another embodiment,dewatering is achieved by centrifugal forces in a perforated bowl orsolid bowl centrifuge.

Mother liquor steam 330 generated in the solid-liquid separation zone300 comprising oxidation solvent, catalyst, and impurities. From 5 wt %to 95 wt %, from 30 wt % to 90 wt %, and most preferably from 40 wt % to80 wt % of mother liquor present in the crude carboxylic acid slurrystream 110 is isolated in solid-liquid separation zone 300 to generatemother liquor stream 330 resulting in dissolved matter comprisingimpurities present in mother liquor stream 330 not going forward in theprocess. In one embodiment, a portion of mother liquor stream 330 isrouted to a mother liquor purge zone 700, wherein a portion is at least5 weight %, at least 25 weight %, at least 45 weight %, at least 55weight % at least 75 weight %, or at least 90 weight %. In anotherembodiment, at least a portion is routed back to the oxidation zone 100,wherein a portion is at least 5 weight %. In yet another embodiment, atleast a portion of mother liquor stream 330 is routed to a mother liquorpurge zone and to the oxidation zone 100 wherein a portion is at least 5weight %. In one embodiment, mother liquor purge zone 700 comprises anevaporative step to separate oxidation solvent from stream 330 byevaporation.

Wash liquor stream 340 is generated in the solid-liquid separation zone300 and comprises a portion of the mother liquor present in stream 210and wash solvent wherein the ratio of mother liquor mass to wash solventmass is less than 3 and preferably less than 2. In an embodiment, atleast a portion of wash liquor stream 340 is routed to oxidation zone100 wherein a portion is at least 5 weight %. In an embodiment, at leasta portion of wash liquor stream 340 is routed to mother liquor purgezone 700 wherein a portion is at least 5 weight %. In anotherembodiment, at least a portion of wash liquor stream is routed tooxidation zone 100 and mother liquor purge zone 700 wherein a portion isat least 5 weight %.

Mother liquor stream 330 comprises oxidation solvent, catalyst, solubleintermediates, and soluble impurities. It is desirable to recycledirectly or indirectly at least a portion of the catalyst and oxidationsolvent present in mother liquor stream 330 back to oxidation zone 100wherein a portion is at least 5% by weight, at least 25%, at least 45%,at least 65%, at least 85%, or at least 95%. Direct recycling at least aportion of the catalyst and oxidation solvent present in mother liquorstream 330 comprises directly routing a portion of stream 330 tooxidizer zone 100. Indirect recycling at least a portion of the catalystand oxidation solvent present in mother liquor stream 330 to oxidationzone 100 comprises routing at least a portion of stream 330 to at leastone intermediate zone wherein stream 330 is treated to generate a streamor multiple streams comprising oxidation solvent and or catalyst thatare routed to oxidation zone 100.

Step (d) comprises separating components of mother liquor stream 330 inmother liquor purge zone 700 for recycle to the process while alsoisolating those components not to be recycled comprising impurities.Impurities in stream 330 can originate from one or multiple sources. Inan embodiment of the invention, impurities in stream 330 compriseimpurities introduced into the process by feeding streams to oxidationzone 100 that comprise impurities. Mother liquor impurities comprise atleast one impurity selected from the following group: 2,5-diformylfuranin an amount ranging from about 5 ppm to 800 ppm, 20 ppm to about 1500ppm, 100 ppm to about 5000 ppm, 150 ppm to about 2.0 wt %; levulinicacid in an amount ranging from about 5 ppm to 800 ppm, 20 ppm to about1500 ppm, 100 ppm to about 5000 ppm, 150 ppm to about 2.0 wt %; succinicacid in an amount ranging from about 5 ppm to 800 ppm, 20 ppm to about1500 ppm, 100 ppm to about 5000 ppm, 150 ppm to about 2.0 wt %; acetoxyacetic acid in an amount ranging from about 5 ppm to 800 ppm, 20 ppm toabout 1500 ppm, 100 ppm to about 5000 ppm, 150 ppm to about 2.0 wt %

An impurity is defined as any molecule not required for the properoperation of oxidation zone 100. For example, oxidation solvent, acatalyst system, a gas comprising oxygen, and oxidizable raw materialcomprising at least one compound selected from the group of formula:5-(hydroxymethyl)furfural (5-HMF), 5-HMF esters (5-R(CO)OCH₂-furfuralwhere R=alkyl, cycloalkyl and aryl), 5-HMF ethers (5-R′OCH₂-furfural,where R′=alkyl, cycloalkyl and aryl), 5-alkyl furfurals (5-R″-furfural,where R″=alkyl, cycloalkyl and aryl), mixed feed-stocks of 5-HMF and5-HMF esters, mixed feed-stocks of 5-HMF and 5-HMF ethers, and mixedfeed-stocks of 5-HMF and 5-alkyl furfurals are molecules required forthe proper operation of oxidation zone 100 and are not consideredimpurities. Also, chemical intermediates formed in oxidation zone 100that lead to or contribute to chemical reactions that lead to desiredproducts are not considered impurities. Oxidation by-products that donot lead to desired products are defined as impurities. Impurities mayenter oxidation zone 100 through recycle streams routed to the oxidationzone 100 or by impure raw material streams fed to oxidation zone 100.

In one embodiment, it is desirable to isolate a portion of theimpurities from oxidizer mother liquor stream 330 and purge or removethem from the process as purge stream 751. In an embodiment of theinvention, from 5 to 100% by weight, of mother liquor stream 330generated in solid-liquid separation zone 300 is routed to mother liquorpurge zone 700 wherein a portion of the impurities present in stream 330are isolated and exit the process as purge stream 751. The portion ofstream 330 going to the mother liquor purge zone 700 can be 5% by weightor greater, 25% by weight or greater, 45% by weight or greater, 65% byweight or greater, 85% by weight or greater, or 95% by weight orgreater. Recycle oxidation solvent stream 711 comprises oxidationsolvent isolated from stream 330 and can be recycled to the process. Theraffinate stream 742 comprises oxidation catalyst isolated from stream330 which can optionally be recycled to the process. In one embodiment,the raffinate stream 742 is recycled to oxidation zone 100 and containsgreater than 30 wt %, greater than 50 wt %, greater than 80 wt %, orgreater than 90 wt % of the catalyst that entered the mother liquorpurge zone 700 in stream 330. In another embodiment, at least a portionof mother liquor stream 330 is routed directly to oxidation zone 100without first being treated in mother liquor purge zone 700. In oneembodiment, mother liquor purge zone 700 comprises an evaporative stepto separate oxidation solvent from stream 330 by evaporation.

One embodiment of mother liquor purge zone 700 comprises routing atleast a portion of oxidizer mother liquor stream 330 to solvent recoveryzone 710 to generate a recycle oxidation solvent stream 711 comprisingoxidation solvent and an impurity rich waste stream 712 comprisingoxidation by products and catalyst. Any technology known in the artcapable of separating a volatile solvent from stream 330 may be used.Examples of suitable unit operations include, but are not limited to,batch and continuous evaporation equipment operating above atmosphericpressure, at atmospheric pressure, or under vacuum. A single or multipleevaporative steps may be used. In an embodiment of the invention,sufficient oxidation solvent is evaporated from stream 330 to result instream 712 being present as a slurry having a weight percent solidsgreater than 10 weight percent, 20 weight percent, 30 weight percent, 40weight percent, or 50 weight percent. At least a portion of impurityrich stream 712 can be routed to catalyst recovery zone 760 to generatecatalyst rich stream 761. Examples of suitable unit operations forcatalyst recovery zone 760 include, but are not limited to, incinerationor burning of the stream to recover noncombustible metal catalyst instream 761.

Another embodiment of mother liquor purge zone 700 comprises routing atleast a portion of mother liquor stream 330 to solvent recovery zone 710to generate a recycle oxidation solvent stream 711 comprising oxidationsolvent and an impurity rich waste stream 712 comprising oxidation byproducts and catalyst. Any technology known in the art capable ofseparating a volatile solvent from stream 330 may be used. Examples ofsuitable unit operations include but are not limited to batch andcontinuous evaporation equipment operating above atmospheric pressure,at atmospheric pressure, or under vacuum. A single or multipleevaporative steps may be used. Sufficient oxidation solvent isevaporated from stream 330 to result in impurity rich waste stream 712being present as slurry with weight % solids greater than 5 weightpercent, 10 weight percent, 20 weight percent, and 30 weight percent. Atleast a portion of the impurity rich waste stream 712 is routed to asolid liquid separation zone 720 to generate a purge mother liquorstream 723 and a wet cake stream 722 comprising impurities. In anotherembodiment of the invention, all of stream 712 is routed to the solidliquid separation zone 720. Stream 722 may be removed from the processas a waste stream. Wash stream 721 may also be routed to solid-liquidseparation zone 720 which will result in wash liquor being present instream 723. It should be noted that zone 720 is a separate and differentzone from zone 300.

Any technology known in the art capable of separating solids from slurrymay be used. Examples of suitable unit operations include, but are notlimited to, batch or continuous filters, batch or continuouscentrifuges, filter press, vacuum belt filter, vacuum drum filter,continuous pressure drum filter, candle filters, leaf filters, disccentrifuges, decanter centrifuges, basket centrifuges, and the like. Acontinuous pressure drum filter is a preferred device for solid-liquidseparation zone 720.

Purge mother liquor stream 723 comprising catalyst and impurities, andstream 731 comprising a catalyst solvent are routed to mix zone 731 toallow sufficient mixing to generate extraction feed stream 732. In oneembodiment, stream 731 comprises water. Mixing is allowed to occur forat least 30 seconds, 5 minutes, 15 minutes, 30 minutes, or 1 hour. Anytechnology know in the art may be used for this mixing operationincluding inline static mixers, continuous stirred tank, mixers, highshear in line mechanical mixers and the like.

Extraction feed stream 732, recycle extraction solvent stream 752, andfresh extraction solvent stream 753 are routed to liquid-liquidextraction zone 740 to generate an extract stream 741 comprisingimpurities and extract solvent, and a raffinate stream 742 comprisingcatalyst solvent and oxidation catalyst that can be recycled directly orindirectly to the oxidation zone 100. Liquid-liquid extraction zone 740may be accomplished in a single or multiple extraction units. Theextraction units can be batch and or continuous. An example of suitableequipment for extraction zone 740 includes multiple single stageextraction units. Another example of suitable equipment for extractionzone 740 is a single multi stage liquid-liquid continuous extractioncolumn. Extract stream 741 is routed to distillation zone 750 whereextraction solvent is isolated by evaporation and condensation togenerate recycle extract solvent stream 752. The purge stream 751 isalso generated and can be removed from the process as a waste purgestream. Batch or continuous distillation may be used in distillationzone 750.

In another embodiment, the source for oxidizer mother liquor stream 330feeding mother liquor purge zone 700 may originate from any motherliquor stream comprising oxidation solvent, oxidation catalyst, andimpurities generated in process to make furan-2,5-dicarboxylic acid(FDCA). For example, a solvent swap zone downstream of oxidation zone100 that isolates at least a portion of the FDCA oxidation solvent fromstream 110 can be a source for stream 330. Suitable equipment for asolvent swap zone comprises solid-liquid separation devices includingcentrifuges and filters. Examples of suitable equipment for the solventswap include, but is not limited to, a disc stack centrifuge or acontinuous pressure drum filter.

EXAMPLES

This invention can be further illustrated by the following examples ofembodiments thereof, although it will be understood that these examplesare included merely for the purposes of illustration and are notintended to limit the scope of the invention unless otherwisespecifically indicated.

Air oxidation of 5-HMF/5-AMF/5-EMF using cobalt, manganese and ionicbromine catalysts system in acetic acid solvent were conducted. Afterreaction the heterogeneous mixture was filtered to isolate the crudeFDCA. The crude FDCA was washed with acetic acid two times and thentwice with DI water. The washed crude FDCA was oven dried at 110° C.under vacuum overnight. The solid and the filtrate were analyzed by GasChromatography using BSTFA derivatization method. b* of the solid wasmeasured using a Hunter Ultrascan XE instrument. As shown in Tables 1 to3 we have discovered conditions that to generate yields of FDCA up to89.4%, b*<6, and low carbon burn (<0.00072 mol/min CO+CO₂)

TABLE 1 Results from semi-batch reactions using 5-HMF feed.* Co conc Mnconc Br conc yield of yield of CO (total CO₂ (total CO_(x) Note-Book No.Example Bromide source (ppm) (ppm) (ppm) FDCA (%) FFCA (%) mol) mol)(mol/min) color (b*) Ex-000250-187 1a solid NaBr 2000 93.3 3000 81.60.81 0.013 0.078 0.000758 13.91 Ex-000186-019 1b solid NaBr 2000 93.33000 82.6 0.87 0.013 0.092 0.000875 14.14 Ex-000186-004 2a aqueous HBr2000 93.3 3000 89.4 0.58 0.003 0.061 0.000533 5.845 Ex-000186-016 2baqueous HBr 2000 93.3 3000 88.6 0.8 0.0037 0.061 0.000539 6.175 *P = 130psig, CO_(x) (mol/min) = CO (mol/min) + CO2 (mol/min).

TABLE 2 Results from semi-batch reactions using 5-AMF feed.* Note BookCo conc Mn conc Br conc Temperature % yield of % yield of CO2 (total #Example (ppmw) (ppmw) (ppmw) (° C.) FDCA FFCA CO (total mol) mol) CO_(x)(mol/min) color (b*) 186-026 2a 2500 116.8 2500 130 88.2 0.25 0.00520.08 0.00071 4.4 186-044 2b 2000 93.5 3000 130 90.2 0.16 0.005 0.0460.000425 6.8 *P = 130 psig, CO_(x) (mol/min) = CO (mol/min) + CO2(mol/min).

TABLE 3 Results from semi-batch reactions using 5-EMF feed.* CO2 NoteBook Co conc Mn conc Br conc Temperature % yield of % yield of % yieldof CO (total (total CO_(x) # Example (ppmw) (ppmw) (ppmw) (° C.) FDCAFFCA EFCA mol) mol) (mol/min) color (b*) 186-028 3a 2500 116.8 2500 13088.8 0.02 0.225 0.008 0.068 0.00063333 3.97 186-031 3b 2000 93.5 3000130 88.0 0.09 0.43 0.008 0.078 0.00071667 2.48 186-034 3c 2000 93.5 3000105 86.0 2.92 1.4 0.005 0.046 0.000425 6.66 186-038 3d 2500 116.8 2500130 87.4 0.42 1.3 0.009 0.064 0.00060833 2.74 *P = 130 psig, CO_(x)(mol/min) = CO (mol/min) + CO2 (mol/min).

Claims not Limited to Disclosed Embodiments

The preferred forms of the invention described above are to be used asillustration only, and should not be used in a limiting sense tointerpret the scope of the present invention. Modifications to theexemplary embodiments, set forth above, could be readily made by thoseskilled in the art without departing from the spirit of the presentinvention.

The inventors hereby state their intent to rely on the Doctrine ofEquivalents to determine and assess the reasonably fair scope of thepresent invention as it pertains to any apparatus not materiallydeparting from but outside the literal scope of the invention as setforth in the following claims.

1. A process to produce a raffinate stream in a method for making acarboxylic acid, said process comprising: (i) oxidizing in an oxidationzone an oxidizable raw material stream comprising5-(hydroxymethyl)furfural (5-HMF) in the presence of an oxidationsolvent stream comprising a saturated organic acid having from 2-4carbon atoms and a catalyst at a temperature of 100° C. to 220° C. toproduce a crude carboxylic acid slurry; wherein said oxidation zonecomprises at least one oxidation reactor; wherein said crude carboxylicacid slurry comprises furandicarboxylic acid; wherein said catalystcomprises cobalt, manganese and bromine; and wherein the yield offurandicarboxylic acid is greater than 60%; (ii) routing said crudecarboxylic acid slurry to a solid liquid separation zone to produce amother liquor stream comprising the catalyst and impurities; (iii)routing at least a portion of the mother liquor stream to a motherliquor purge zone comprising a mixing zone and a liquid-liquidextraction zone; (iv) mixing at least a portion of the mother liquidstream with a catalyst solvent in the mixing zone to generate anextraction feed stream; and (v) contacting the extraction feed streamwith an extraction solvent stream in the liquid-liquid extraction zoneto generate an extract stream comprising the impurities and theextraction solvent, and a raffinate stream comprising the catalyst andthe catalyst solvent.
 2. The process according to claim 1 wherein saidcatalyst comprises cobalt in a range from about 500 ppm by weight toabout 6000 ppm by weight with respect to the weight of the liquid in thereaction medium, manganese in an amount ranging from about 2 ppm byweight to about 600 ppm by weight with respect to the weight of theliquid in the reaction medium, and bromine in an amount ranging fromabout 300 ppm by weight to about 4500 ppm by weight with respect to theweight of the liquid in the reaction medium.
 3. The process according toclaim 1 wherein said oxidation reactor is a bubble column.
 4. Theprocess according to claim 1 wherein said catalyst comprises cobalt in arange from about 700 ppm to about 4500 ppm by weight with respect to theweight of the liquid in the reaction medium, manganese in an amountranging from about 20 ppm by weight to about 400 ppm by weight withrespect to the weight of the liquid in the reaction medium, and brominein an amount ranging from about 700 ppm by weight to about 4000 ppm byweight with respect to the weight of the liquid in the reaction medium.5. The process according to claim 1 wherein said catalyst comprisescobalt in a range from about 1000 ppm to about 4000 ppm with respect tothe weight of the liquid in the reaction medium, manganese in an amountranging from about 20 ppm to about 200 ppm by weight with respect to theweight of the liquid in the reaction medium and bromine in an amountranging from about 1000 ppm to about 4000 ppm by weight with respect tothe weight of the liquid in the reaction medium.
 6. The processaccording claim 1 wherein said crude carboxylic acid slurry furthercomprises 5-formyl furan-2-carboxylic acid (FFCA).
 7. The processaccording claim 1 wherein said oxidizing is conducted at a temperaturefrom 105° C. to 180° C.
 8. The process according claim 1 wherein saidoxidizing is conducted at a temperature from 110° C. to 160° C.
 9. Theprocess according to claim 1 wherein said oxidizable raw material streamcomprises greater than 2% by weight of 5-HMF.
 10. The process accordingto claim 1 wherein said oxidizable raw material stream comprises greaterthan 20% by weight of 5-HMF.
 11. The process according to claim 1wherein said oxidizable raw material stream comprises greater than 50%by weight of 5-HMF.
 12. The process according to claim 1 wherein saidoxidizable raw material stream comprises greater than 70% by weight of5-HMF.
 13. The process according to claim 10 wherein the weight ratio ofcobalt to manganese is about 400 to about
 1. 14. The process accordingto claim 10 wherein the weight ratio of cobalt to manganese is about 40to about
 1. 15. The process according to claim 10 wherein the weightratio of cobalt to manganese is about 30 to about
 1. 16. The processaccording to claim 10 wherein the weight ratio of cobalt to manganese isabout 20 to about
 1. 17. The process according to claim 10 wherein theweight ratio of cobalt to manganese is about 10 to about
 1. 18. Theprocess according to claim 13 wherein the weight ratio of cobalt tobromine about 0.75 to about 3.5.